The present invention relates to a fast neutron nuclear reactor of the type having a cylindrical inner vessel.
More specifically, the present invention relates to a fast neutron nuclear reactor of the integrated type and which is more particularly cooled by a liquid metal such as liquid sodium or other equivalent liquid metals.
It is known that in fast neutron nuclear reactors of the integrated type cooled by a liquid metal, the known vessel containing the liquid cooling metal contains an inner vessel, whose main function is to separate on the one hand the hot sodium leaving the core of the reactor contained in the inner vessel and on the other the cold sodium leaving the exchangers disposed in the annular space between the inner vessel and the main vessel.
Various inner vessel arrangements have been proposed to bring about this separation. Reference is firstly made to so-called ridged inner vessels in which the ridge, traversed by the intermediate exchangers, makes it possible to separate the exchanger intake which is supplied by the sodium from the core and the exchanger outlet which issues into the annular space containing the primary pumps.
Another solution consists of using a generally cylindrical inner vessel. In this case, pipes connect the interior of the inner vessel above the core to the intake of the intermediate exchangers, which are themselves surrounded by a collar or ferrule.
This type of reactor is in particular described in French patent application No. 75 39982 of Dec. 29, 1975 in the name of the present Applicant. In the case of this type of inner vessel, there is an annular space between the external periphery of the core or more specifically its lateral neutron protection and the inner part of the inner vessel. In this annular space, there are convection movements of the hot sodium leaving the core and which can be prejudicial to the mechanical behaviour of structures such as the girder or support which supports the core and the flooring on which said girding or support rests. Thus, problems are encountered in the heating of such structures and it is necessary to provide means for preventing convection movements.
Another disadvantage of such a design is that the pipe which guides the hot liquid metal between the interior of the inner vessel and the heat exchangers are directly fixed to the inner vessel. The hot liquid metal flow in such pipes leads to vibrations, which are thus transmitted to the assembly constituted by the inner vessel and its support.